No mention is made of the anemometer or any other
gauge of the result asserted, and we are left to the suspicion that it
is merely a matter of theoretical inference, as usual; for every one
who has had any acquaintance with practical tests in these matters
knows that no such movement of air ever takes place under such
conditions, unless by exceptional favor of the weather.
I have seen a tall steam boiler chimney induce through a four inch
pipe a suction strong enough to exhaust the air from a large room as
fast as perfect ventilation would require. But this, it is well known,
requires four hundred or five hundred degrees of heat in the chimney.
I never saw an ordinary domestic fire of coals produce any noticeable
ventilating suction, without the use of a blower, urging the
combustion to fury, and I presume nobody else ever did.
But, while nobody ever saw an active suction of air produced by the
mere heat of a still or unexcited fire--unless the _quantity_ of heat
were on a very large scale--everybody has seen a roaring current
sucked through the narrowed throat of a chimney or a stove by a
blazing handful of shavings, paper, or straw. It is very remarkable,
when you come to think of it, that the burning of an insignificant
piece of paper, with less heat in it, perhaps, than a pea of
anthracite, will cause a rush of air that a bushel of anthracite
cannot in the least degree imitate. It is not only a curious but a
most important fact. In short, it is _the cardinal_ fact on which
ventilation practically turns.
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